Efficient mercury removal from aqueous solutions using carboxylated Ti3C2Tx MXene
2022
Isfahani, Ali Pournaghshband | Shamsabadi, Ahmad A. | Alimohammadi, Farbod | Soroush, Masoud
Water supplies contaminated with heavy metals are a worldwide concern. MXenes have properties that make them attractive for the removal of metal ions from water. This work presents a simple one-step method of Ti₃C₂Tₓ carboxylation that involves the use of a chelating agent with a linear structure, providing strong carboxylic acid groups with high mobility. The carboxylation decreases the zeta-potential of Ti₃C₂Tₓ by ~16 to ~18 mV over a pH range of 2.0–8.5 and improves Ti₃C₂Tₓ stability in the presence of molecular oxygen. pH in the range of 2–6 has a negligible effect on the adsorption capacity of Ti₃C₂Tₓ and COOH–Ti₃C₂Tₓ. Compared to Ti₃C₂Tₓ, COOH–Ti₃C₂Tₓ has a slightly higher and much faster mercury uptake, and the concentration of mercury ions leached out from COOH-Ti₃C₂Tₓ is lower. For both Ti₃C₂Tₓ and COOH–Ti₃C₂Tₓ, the leached mercury ion concentration is far below the U.S.-EPA maximum level. At an initial Hg²⁺ concentration of 50 ppm and pH of 6, COOH–Ti₃C₂Tₓ has the equilibrium adsorption capacity of 499.7 mg/g and removes 95% of Hg²⁺ in less than 1 min. Moreover, it has an equilibrium time of 5 min, which is significantly shorter than that of Ti₃C₂Tₓ (~ 60 min). Finally, its mercury-ion uptake capacity is higher than commercially available adsorbents reported in the literature. Its mercury removal is mainly via chemisorption and monolayer adsorption.
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